Features of Profiles for Currents, Momentum Flux, and a Turbulence Dissipation Rate in Wind-Wave Channel

Abstract

Vertical profiles of the mean horizontal currents U(z), the vertical momentum fluxes τ(z), and the turbulence kinetic-energy dissipation rates (TKE dissipation rate) e(z) in the upper water layer (UWL) are considered and their joint analysis is carried out. For this purpose, data from laboratory measurements performed in the wind-wave channel of the Institute of Applied Physics, Russian Academy of Sciences (RAS) [1, 2], are used. They correspond to conditions of strong wind and breaking wind waves. The profiles of the currents and momentum fluxes are estimated for x and z components of the velocity at five horizons in the UWL at four various wind values. The empirical estimates of e(z) obtained from the same data in the previous work [3] are used in the joint analysis. It is established that (a) velocity of currents U(z) increases noticeably when compared to the values of U(z) in the absence of waves, (b) the momentum flux in the water τw(z) decreases noticeably when compared to that in the air τa(z), and (c) τw(z) significantly attenuates with depth according to ratio τw(z) ~ 1/z2. The mentioned anomalies of profiles U(z) and τ(z) in the UWL are analyzed together with the previously determined pattern of TKE dissipation-rate falloff with depth according to ratio e(z) ~ 1/z2 in order to search for an interpretation of the results.